Also Alternative fuels

CNG, compressed natural gas, and LPG, liquefied petroleum gas, are also used as alternative fuels. 

Most urban rail service is electric-powered and most urban bus service is diesel-powered, although diesel rail and electric bus operations do exist, as noted above. The efficiency and environmental impacts of electricity depend gi eatly on the source of electric power. Although electric vehicles produce no tailpipe emissions, generation of electricity can produce significant emissions that can travel long distances, Eor example, coal-powered electricity plants produce particulate emissions that travel halfway across North America, Urban buses also can be powered by a variety of alternative fuels. 

In 1991 the California Air Resources Board certified a compressed natural gas (CNG) powered engine as the first alternative fueled engine certified for use in California. The board also sponsored a program to fuel school buses with CNG. While CNG has been used for fleet and delivery vehicles, most tanks hold enough fuel for a little over 100 miles. 

The AMFA had demonstration programs to promote the use of alternative fuels and alternative-fuel vehicles. The act also offered credits to automakers for producing alternative-fuel vehicles and incentives to encourage federal agencies to use these vehicles. 

Technological changes in the manufacture of power sources are required if they are to run on alternative fuels. The development of alternative fuels depends on automotive manufacturers making alternative fuel engines available while fuel suppliers produce and distribute fuels for these vehicles. Flexible fuel vehicles (FFVs), which are also known as variable fuel vehicles, (VFVs) are designed to use several fuels. Most of the major automobile manufacturers have developed FFV prototypes and many of these use ethanol or methanol as well as gasoline. 

Methanol also seems to biodegrade quickly when spilled and it dissolves and dilutes rapidly in water. It has been recommended as an alternative fuel by the EPA and the DOE, partly because of reduced urban air pollutant emissions compared to gasoline. Most methanol-fueled vehicles use a blend of 85% methanol and 15% gasoline called M85. Building a methanol infrastructure would not be as difficult as converting to hydrogen. While methanol can be produced from natural gas, it can also be distilled from coal or even biomass. In the 1980s, methanol was popular for a brief time as an internal-combustion fuel and President Bush even discussed this in a 1989 speech. 

A cogeneration system may use different fuels including natural gas, residual fuel oil, heating oil, diesel fuel and gasoline. Alternate fuel sources also include coal liquids or wood gas. 

The United States passed the Energy Policy Act in 1992. One goal was to reduce the amount of petroleum used for transportation by promoting the use of alternative fuels in cars and light trucks. These fuels included natural gas, methanol, ethanol, propane, electricity, and biodiesel. Alternative fuel vehicles (AFVs) can operate on these fuels and many are dual fueled also running on gasoline. 

Similar actions are to be observed in other parts of the world, increasingly with the objective of diversifying the fuel supply in the transport sector. Examples are in Brazil, which has the world s most developed biofuel industry, and where a 25% blend (mainly ethanol) is mandatory, or the Alternative Fuel Standard (AFS) at federal level in the USA, or various biofuel mandates being introduced at state level (see also (EC, 2006b)). 

Well-to-wheel analysis is a specific form of life-cycle analysis (LCA). In contrast to WTW analysis, LCA typically also takes factors other than global GHG emissions of a product or an energy carrier into consideration (such as air pollutants), including provision of all construction materials for the necessary processing plants and, furthermore, plant decommissioning. The full detail of a general LCA analysis is not needed at the level of policy discussion to reach a broad consensus on alternative fuels or drive systems. As a subset of WTW analysis, well-to-tank (WTT) analysis is often used to separate environmental or economic effects of fuel supplies and drive systems. 

---